The article mentions that the Python handler is run outside of the C handler context and so is not subject to the C safety restrictions. It will not crash since the interpreter only calls the Python handler when it is safe. It will however not protect against reentrancy issues in the Python handler.

The C printf function is not async signal safe and is one of the examples in the manual: https://man7.org/linux/man-pages/man7/signal-safety.7.html